Generally, when putting on the brake with a great frequency, such as on a downhill road, an engine brake is used in combination. However, in a large vehicle, such as a truck or a bus, the weight is originally heavy and the loading weight is applied. Hence, when the loading weight is heavy or the downhill road is steep, the effect of the engine brake may be inefficient.
Therefore, a compression release brake capable of obtaining a strong braking force during engine braking is supplementarily used. The compression release brake inhibits the generation of a force to push down a piston during an expansion stroke by forcibly opening an exhaust valve and releasing a compressive pressure near a compression top dead center of an engine, so that a braking force obtained during a compression process effectively acts.
Further, as citation list information related to the invention of this application, there are Patent Documents 1 to 4 and Non Patent Document 1.